Can the Head Coach call a Hail Mary or an all go on the final play in regulation if the team is outside field goal range and either tied or down by up to three points or anywhere on the field if down by 4 to 8 points, with a D auto setting to a Prevent type defense.

If you try to set a default rule for this you are limited to the final 30 seconds when a team can have 3 or 4 plays, if they have timeouts.

Too many times games are ended around the 50 yard line with a QB throwing a screen pass behind the line of scrimmage.

it would generally be very good, if the QB will have situational awareness when making his decision where to go with the ball.
down and distance, time remaining and score and defenders around the target should have way more influence on the decision where to go with the ball than it seems to be the case now